He is a depressed, yet intelligent teenager who doesn't have much time to live due to his genetic disease. He has realized the finality of his death, and doesn't bother with denial or hope. Though he never finishes them, he finds solace in his books, and decides to write his own story about finding the meaning of life. Initially he is rather aloof as he hates being pitied for his illness, but quickly warms up to the player. During the course of the social link, Akinari stops taking his medication, claiming that they were only speeding up the process, and that he needed to finish writing his story before he died.

Also known as the Dying young man, Akinari represents the Sun social link in Persona 3. He is first seen at Naganaki Shrine, where he is playing with Maiko. The social link is initiated by the protagonist speaking to Akinari on a Sunday (the only day he is available) at Naganaki Shrine, then speaking to Koromaru in the dorm after he has joined SEES, and receiving Akinari's red fountain pen, then returning the pen to Akinari. However, the Social Link with him is only available if the protagonist's Academics have reached the Smart rank. Akinari is a teenager who has been diagnosed with an incurable, life-threatening genetic disease, and isn't expected to live much longer. As such, his outlook on life is bleak. He finds it hard to identify with normal, healthy people, but eventually comes to enjoy the company of the protagonist, and looks forward to his visits every Sunday afternoon.

As the social link progresses, Akinari begins to write a story about a bird and an alligator that begins happy, but he has trouble ending it on a happy note, at one point deciding to end it with the alligator accidentally swallowing the bird, and being sad about his unfortunate actions for the rest of his life. Later, Akinari decides that life is worth living to its fullest, and finishes the story on a happy note.

At the end of the link, Akinari gives his notebook with his story in it for the protagonist to keep, with his final wish granted, he smiles and bids the protagonist farewell, disappearing into the sunlight before the protagonist's eyes.

If the protagonist visits the shrine on one of the final days of the game, he/she will meet Mrs. Kamiki, Akinari's mother. She reveals (on whichever day the protagonist visits her) that it would be Akinari's twentieth birthday if he were still alive. Akinari's mother laments that he couldn't live his adulthood, but before his death, Akinari thanked his mother for birthing him and taking care of him, and said was glad to be born. These words by Akinari give his mother the resolve to push forward in life. Akinari's mother then mentions the story Akinari was writing, and wonders if he gave the protagonist the notebook. Upon finding that he did, Akinari's mother is relieved; she knows his dream was fulfilled, and he reached his goal before he died. She vows to experience new things to tell her son on the day they meet together in the afterlife before parting from the protagonist.

Akinari represents the Sun Arcana Social Link, which can be accessed once players' progress the Hanged Man Social Link to level 3. He can be contacted on Sunday, and upon visiting him, the protagonist must return to the dorm to retrieve Akinari's red fountain pen from Koromaru. Akinari can be found at Naganaki Shrine, sitting on the playground's bench. Upon completing the Social Link, Akinari will give the protagonist his notebook, bestowing the ultimate form of the Sun arcana, Asura.

NB : Does not require a Persona of the Sun Arcana to level up his Social Link.

During an Emperor ArcanaSocial Link scene, Kanji mentions a "pink alligator, like in that storybook", alluding to Akinari's social link. Later in Persona 4 Golden it is alluded to again when Nanako reads a storybook about a pink alligator during the Jester ArcanaSocial Link.

Akinari died at 19 years old, 19 (XIX) being the number of the Sun Arcana.